Maria Sharapova has been forced to pull out of the Miami Open because of an injury to her forearm.

Sharapova has endured a disappointing 2018 season - her first full campaign since returning from a doping ban last year - exiting the Australian Open in the third round before losing to Monica Niculescu and Naomi Osaka in her first matches at the Qatar Open and Indian Wells Masters respectively.

The Russian, who has since split with long-time coach Sven Groeneveld, is a five-time finalist in Miami but will not have the opportunity to end her wait for a first win at the tournament.

"I am really sorry that I have to withdraw from one of my favourite tournaments with my left forearm injury. I am doing everything possible to return to the tour as soon as possible," Sharapova said.

Tournament director James Blake added: "I know how much Maria wanted to play Miami this year, so I can imagine her disappointment.

"We were looking forward to seeing her play Wednesday, but unfortunately injuries are part of the game. We hope she recovers quickly and is back on the court soon."

Sharapova, who won her first WTA title for two years at the Tianjin Open last October, is ranked 41st in the world.

Her place in the main draw has been taken by Jennifer Brady.